The petroleum industry is increasingly turning to heavy crudes, resids, coals and tar sands as sources for feedstocks. Feedstocks derived from these heavy materials contain more sulfur and nitrogen than feedstocks derived from more conventional crude oils, requiring a considerable amount of upgrading in order to obtain usable products therefrom. These heavier and high sulfur crudes and resides also present problems as they invariably also contain much higher metals contaminant metals such as nickel, vanadium, and iron, which represent operating problems in terms of metal deposit/build-up in the equipment.
The upgrading of heavy oil feedstock is accomplished by hydrotreating processes, i.e., treating with hydrogen of various hydrocarbon fractions, or whole heavy feeds, or feedstocks, in the presence of hydrotreating catalysts to effect conversion of at least a portion of the feeds, or feedstocks to lower molecular weight hydrocarbons, or to effect the removal of unwanted components, or compounds, or their conversion to innocuous or less undesirable compounds.
Catalysts commonly used for these hydrotreating reactions include materials such as cobalt molybdate on alumina, nickel on alumina, cobalt molybdate promoted with nickel, nickel tungstate, at least a group VIB metal compound with at least a promoter metal compound, etc. High catalyst dosage will improve the conversion rate and reduce solid accumulation in the process equipment. However, there is an economic limitation as how much catalyst can be used, as a high dosage will drive up capital and operating costs.
There is still a need for improved catalysts with balanced material costs, while still offering excellent morphology, structure and catalytic activity. There is also a need for improved processes to prepare catalysts for use in the conversion of heavy oils and residua. There is a further a need for improved heavy oil upgrade processes with reduced build-up of heavy metal contaminants.